As you can see, you need to pass several references to global objects as well as a WlSeat.
It is required for the library to be able to create the surfaces to draw the borders, react
to user input in the borders, for resizing and move. It will use the events provided on the
seat you passed as argument. (So if you are on a setup with more than one pointer,
only the one associated with this seat will be able to resize the window).

See next section for example use of the my_implementation and
my_implementation_data arguments.

Configure events

The Frame object will not resize your window itself, as it cannot do it.

When the user clicks on a border and starts a resize, the server will start to generate a
number of configure events on the shell surface. You'll need to process the events generated
by the surface to handle them.

The wayland server can (and will) generate a ton of configure events during a single
WlDisplay::dispatch() if the user is currently resizing the window. You are only required to
process the last one, and if you try to handle them all your aplication will be very
laggy.

The proper way is to accumulate them in your subhandler, overwriting the the previous one
each time, and manually checking if one has been received in the main loop of your program.
For example like this

Resizing the surface

When resizing your main surface, you need to tell the Frame that it
must update its dimensions. This is very simple:

// update your contents size (here by attaching a new buffer)
surface.attach(Some(&new_buffer));
surface.commit();
// update the borders size
frame.resize(width, height);
// refresh the frame so that it actually draws the new size
frame.refresh();

If you do this as a response of a configure event, note the following points:

You do not have to respect the exact sizes provided by the compositor, it is
just a hint. You can even ignore it if you don't want the window to be resized.

In case you chose to ignore the resize, it can be appropiate to still resize your
window to its current size (update the buffer to the compositor), as the compositer
might have resized your window without telling you.

The size hint provided to your implementation is a size hint for the interior of the
window: the dimensions of the border has been subtracted from the hint the compositor
gave. If you need to compute dimensions taking into account the sizes of the borders,
you can use the add_borders and subtract_borders functions.